Wrargh! I was finally able to get what I wanted, but i have to use unreliable means of achieving this effect. For anyone even remotely interested, and for my future reference, here is what I came up with to get the "Arwing tilt and spin" system to work without using animation registers.
http://strouperman.com/Special/StarFox_ ... mation.cap
(if you get 404, add the www)
To test it:
Arwing moves with WSAD
Tilt the ship left with LEFT SHIFT
Tilt the ship right with J
Fire lasers with G (numbers 1, 2, and 3 change laser type)
To do a barrel roll
, double-tap the tilt buttons.
::Arwing moves faster in the direction of tilt.
::Arwing moves slower opposite direction of tilt.
::Spinning the Arwing temporarily super-spikes movement acceleration.
Combining these techniques allows for a (hopefully) tight and precise control scheme.